Project Description
For nearly two decades, there has been growing interest in the identification of “green” alternatives to conventional organic solvents, whose volatility and toxicity frequently render them environmentally problematic. One such alternative, “deep-melting eutectics” (DMEs; also known as “deep-eutectic solvents”), form upon mixing certain organic solids capable of hydrogen-bonding interactions. The result of these interactions is a significant decrease in the melting point of the mixture relative to the initial organic solids, the extent of which varies with the precise nature of the mixture (i.e., the mixture constituents and their proportions). By proper choice of components, ambient-temperature liquids that are biodegradable or environmentally benign can be obtained.
Unfortunately, to date, the practical utility of these novel liquids has been limited, a result of their significant water solubility. Recently, however, evidence has emerged to indicate that hydrophobic (i.e., water-immiscible) eutectics (dubbed HDMEs) can also be prepared, thus making possible the use of these solvents as the basis of two-phase systems for catalysis and separations. Our objective is to examine the factors governing the physicochemical properties of HDMEs, in particular their melting points and water solubility, and to explore their use in the extraction of toxic metals and organics from water.
Tasks and Responsibilites
The student will prepare and characterize (water solubility, water content, thermal properties) a series of HDMEs comprising various combinations of hydrogen bond acceptors (e.g., quaternary ammonium halides) and donors (e.g., carboxylic and phosphoric acids). For donor-acceptor combinations found to yield an HDME with low water solubility, a sub-ambient melting point, and good thermal stability, the eutectics will be evaluated as solvents for the extraction of representative toxic metal ions (.e.g., Pb2+, Cd2+) and organics (e.g., phenols, dyestuffs) from aqueous solution.